1. Field of Invention
The present invention relates to antistatic hoses for conveyance of gases, liquids, or powders capable of producing and accumulating static electricity, and more particularly to mechanisms contained within such hoses for dissipating such static electricity accumulations.
2. Description of the Prior Art
Those skilled in the art will appreciate typical issues related to avoidance of accumulations of static electricity in hoses used to convey volatile fluids, including gases, liquids, and powders. Numerous efforts have been made, as are represented in the prior art, with respect to designs of composite hose and fiber structures capable of successfully minimizing the accumulations of static electricity over the useful life of a given hose.
Significant efforts have been directed to dissipation of such accumulations, and particularly with respect to grounding means for handling an otherwise uncontrollable buildup of static electricity generated along the structure of a hose or tube. Many efforts have been directed to the manufacture of plastic and rubber hoses that are made semi-conductive via inclusion of particles of carbon embedded in the structure of elastomers, for example. In some cases, metallic wires have been installed over the elastomer hose via braided, spiral, or helically wound structures applied about at least a portion of the hose or tube. In each of such instances, it has always been necessary to achieve electrical grounding of such wires or braids, thus generally requiring some type of multiple pronged plate or circular ring installed in the end of the hose or tube to provide satisfactory electrical grounding.
One particularly difficult issue with respect to the use of metallic members for imparting conductivity has been the high flexural moduli of metallic wires, resulting in their tendencies to break upon repeated flexing, with resultant loss of electrical conductivity.
The present invention provides an improved apparatus for a hose, the apparatus adapted to impart electrical conductivity to a rubber or elastomer layered hose member. The present invention assures conductivity for dissipating static electrical charges, while being resistant to fatigue and breakage under conditions of repeated bending and flexing of the hose member.
In a first described embodiment, the hose is a composite structure that includes a conductive fiber strand extending contiguously from one end of the hose to the other. The conductive fiber strand is covered with silver plating, and is a silver-plated nylon material in the described embodiment. The nylon provides a flexible medium not readily prone to breakage, while the silver plating provides a relatively low electrical resistance due to its relatively high electrical conductivity, for avoiding the potentially lethal effects of static electricity buildup.
Also in the described embodiment, the hose includes an inner (innermost) layer of an insulation material, such as rubber. An electrically conductive fiber strand is applied over the inner layer in a spiral pattern, and an outer cover material is extruded over the hose inner layer and the fiber strand. In an alternate embodiment, the hose includes a textile braided yarn layer positioned directly above the strand over the inner layer, immediately beneath the outer cover.